A federal judge Thursday refused to halt construction on the controversial Willits Bypass highway project, after environmental groups had requested a preliminary injunction in September.

The proposed four-lane freeway would reroute U.S. Highway 101 around the downtown Willits area, and has caused controversy with environmental groups who say the project would harm wetlands, salmon streams and endangered plants. The groups have a pending lawsuit challenging the permits and approvals of the project, but that won't be heard until December, a press release from the Environmental Protection Information Center in Arcata said.

The motion for a preliminary injunction was requested by the Center for Biological Diversity, Willits Environmental Center, Redwood Chapter of the Sierra Club and EPIC.

The court agreed there is a risk of environmental harm in allowing cutting of legacy oak trees and riparian vegetation to continue forward before the trial, but its ruling allows Caltrans to initiate the construction process, the release said.

"We will press forward with our lawsuit against this ill-conceived highway project," said Ellen Drell, of the Willits Environmental Center in the release. "We cannot allow Caltrans and the Army Corps of Engineers to use taxpayer money for such extensive damage to our environment just because one intersection in Willits backs up for a few hours a day."

"We are pleased with today's ruling denying the requested injunction," said Charlie Fielder, Caltrans District 1 Director, in a press release from his agency. "Our extensive mitigation plans not only preserve native species and improve the quality of the watershed in the Little Lake Valley, they will also greatly increase the overall quality of fisheries in these headwaters of the Eel River."

According to a previous statement issued by Caltrans, the proposed four-lane bypass project will relieve congestion, reduce delays, and improve safety for traffic currently passing through Willits, eliminating the only stoplights on Highway U.S. 101 between San Francisco and Eureka.